The present invention relates to a method and apparatus for teeming molten metal into a vertical sleeve in a vertical die casting machine.
Die casting machines are classified into a vertical clamping type machine and a horizontal clamping type machine according to a clamping direction. They are also classified into a vertical casting type machine and a horizontal casting type machine according to a casting direction. Of these types of machines, the horizontal clamping/vertical die casting machine is generally constituted as follows.
A pair of stationary platens are arranged upright on a machine base so as to oppose each other and are connected by tie rods at their four corners. A movable platen is supported on the tie rods so as to be movable forward/backward in a direction to move close to or away from one stationary platen. Movable and stationary metal molds are respectively mounted on the movable platen and one stationary platen. A cavity is formed in a joining portion of the stationary metal mold and the movable metal mold which is moved together with the movable platen by a clamping cylinder on the side of the other stationary platen so as to perform clamping. A stationary sleeve communicating with the cavity is fitted in the stationary metal mold so as to open below. An injection apparatus is supported below the stationary metal mold so as to be set upright/tilted or laterally moved. The injection apparatus comprises an injection cylinder secured to an injection frame, and a plunger coupled to a piston rod of the cylinder and having a plunger chip fitted in a vertically movable injection sleeve arranged on the injection frame.
When a molten metal is to be supplied to the injection apparatus having such an arrangement, the entire injection apparatus is titled, and a molten metal supplying operation is performed by a molten metal supply apparatus. In this case, the supplying operation is started while the plunger chip is set at the highest position. As the operation proceeds, a predetermined amount of molten metal is teemed while only the plunger chip is lowered without changing the position of the injection sleeve, or is teemed while the plunger chip is set at the lowest position.
When the supplying operation is completed in this manner, the injection apparatus is set upright to bring the injection sleeve into contact with the stationary sleeve. The plunger chip of the injection cylinder is moved upward to inject the molten metal into the cavity via the stationary sleeve. Thereafter, the molten metal is solidified and a cast product is obtained.
If, however, only the plunger chip is lowered to supply a molten metal into the injection sleeve, in addition to a molten metal contact surface coated with a mold release agent, a non-coated portion is exposed to cause seizing. Alternatively, if a molten metal is supplied from a high position, inclusion of a gas or oxides may occur.